Understanding cancer
Cancer is not one disease. It is a large group of diseases in which abnormal cells grow without normal control, may invade nearby tissue and sometimes spread to other parts of the body.
How cancer begins
Cells normally grow, divide and die according to carefully controlled signals. Changes in DNA can disrupt those signals. A cell may begin dividing when it should not, resist normal cell death or evade the immune system.
Key words
- Primary cancer: where a cancer first began.
- Metastasis: cancer cells spreading to a distant site.
- Grade: how abnormal tumor cells look.
- Stage: how much cancer is present and where it is.
- Remission: signs and symptoms are reduced or absent.
What causes these changes?
Inherited changes
Some people inherit gene variants that raise risk, but an inherited risk does not mean cancer is certain.
Changes over time
DNA changes can accumulate as cells divide and as people age.
Exposures and infections
Tobacco, ultraviolet radiation, some chemicals and certain infections can contribute to risk.
Cancer is not contagious. A diagnosis is not a personal failure, and often no single cause can be identified.